What system shares similarities with NFC but is mainly used for tracking and authentication?

Radio Frequency Identification (RFID) is the correct answer because it operates on the same principle of using radio waves to communicate between a reader and a tag. While NFC is essentially a subset of RFID technology designed for short-range communication (typically up to 4 inches), RFID systems can work over longer distances, depending on the frequency and type of tags used.

RFID is primarily used for tracking objects and authentication purposes. It is widely implemented in inventory management, access control systems, and supply chain logistics. The tags can be passive (powered by the reader's signal) or active (having their own power source), thus enabling a range of applications where tracking and authentication are critical.

In contrast, while Bluetooth is also a wireless technology, it is typically used for connecting devices over longer distances for purposes such as file transfer, audio streaming, or device pairing, rather than primarily for tracking or authentication. NFC, though similar to RFID, is designed for direct device-to-device communication rather than extensive tracking systems. Lastly, a geosynchronous satellite is unrelated to local tracking or authentication; it mainly provides communication or data from space to ground-based receivers.